/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core.codec;

import org.reactivestreams.Publisher;
import org.springframework.core.ResolvableType;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.lang.Nullable;
import org.springframework.util.MimeType;
import org.springframework.util.MimeTypeUtils;
import reactor.core.publisher.Flux;

import java.util.Map;

/**
 * Simple pass-through decoder for {@link DataBuffer DataBuffers}.
 *
 * <p><strong>Note:</strong> The data buffers should be released via
 * {@link org.springframework.core.io.buffer.DataBufferUtils#release(DataBuffer)}
 * after they have been consumed. In addition, if using {@code Flux} or
 * {@code Mono} operators such as flatMap, reduce, and others that prefetch,
 * cache, and skip or filter out data items internally, please add
 * {@code doOnDiscard(PooledDataBuffer.class, DataBufferUtils::release)} to the
 * composition chain to ensure cached data buffers are released prior to an
 * error or cancellation signal.
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @since 5.0
 */
public class DataBufferDecoder extends AbstractDataBufferDecoder<DataBuffer>
{

    public DataBufferDecoder()
    {
        super(MimeTypeUtils.ALL);
    }


    @Override
    public boolean canDecode(ResolvableType elementType, @Nullable MimeType mimeType)
    {
        return (DataBuffer.class.isAssignableFrom(elementType.toClass()) && super.canDecode(elementType, mimeType));
    }

    @Override
    public Flux<DataBuffer> decode(Publisher<DataBuffer> input, ResolvableType elementType, @Nullable MimeType mimeType, @Nullable Map<String, Object> hints)
    {

        return Flux.from(input);
    }

    @Override
    protected DataBuffer decodeDataBuffer(DataBuffer buffer, ResolvableType elementType, @Nullable MimeType mimeType, @Nullable Map<String, Object> hints)
    {

        if (logger.isDebugEnabled())
        {
            logger.debug(Hints.getLogPrefix(hints) + "Read " + buffer.readableByteCount() + " bytes");
        }
        return buffer;
    }

}
